A person playing a first-person shooter video game, such as Halo or Unreal Tournament, must make decisions quickly. Researchers found that the fast-paced decision-making boosts the player's visual skills but comes at a cost, reducing their ability to inhibit impulsive behaviour.

The reduction in what is called "proactive executive control" appears to be yet another way that violent video games can increase aggressive behaviour, according to the researchers.

Doctor Craig Anderson, director of the Centre for the Study of Violence at Iowa State University in the United States, said: "We believe that any game that requires the same type of rapid responding as in most first-person shooters may produce similar effects on proactive executive control, regardless of violent content.

There is a growing body of research that links violent video games, and to a certain extent total screen time, to attention-related problems and aggression.

Dr Anderson said people's ability to override aggressive impulses is dependent in large part on good executive control capacity.

Social psychologists are looking how a variety of factors - including media exposure, anger, and alcohol - affect that capability.

Dr Anderson explained that two types of cognitive control processes play a large role: proactive and reactive.

He said: "Proactive cognitive control involves keeping information active in short-term memory for use in later judgments, a kind of task preparation. Reactive control is more of a just-in-time type of decision resolution."

In three new, unpublished studies, Dr Anderson and his colleagues found that playing action video games is associated with better visuo-spatial attention skills, but also with reduced proactive cognitive control.

He said: "These studies are the first to link violent video game play with both beneficial and harmful effects within the same study."

In one of the studies, Dr Anderson's team had participants - none of whom were frequent gamers - either play the fast-paced and violent video game Unreal Tournament, the slow-paced game Sims 2, or nothing for 10 sessions, each 50 minutes long over the course of 11 weeks.

His team tested the participants' proactive cognitive control and visual attention before and after the video game playing. They found marked decreases in proactive cognitive control among the action game players versus the Sims players or non-game players. At the same time, there were marked increases in the visual attention skills of action gamers.

In another study, Dr Anderson and Edward Swing, also of Iowa State University, assessed the TV and video game habits of 422 people to further examine the links between screen time and attention-related problems and aggression.

In keeping with past research in this area, they found that total media exposure and violent media exposure both contributed directly to attention problems. Violent media exposure had a direct association with greater aggression and anger/hostility, while total media exposure was not significantly related to aggression or anger/hostility.

The analyses looked at both premeditated and impulsive aggression.

Dr Anderson said: "Impulsive aggression, by definition, is aggressive behaviour that occurs automatically, or almost automatically, without evidence of any inhibition or thought about whether it should be carried out."

They found significant links between both types of aggression and attention problems, although the link between attention and premeditated aggression was weaker than the link between attention and impulsive aggression.